The present invention relates to an image transfer device that transfers an image formed on an image receiving sheet on paper by overlapping the image receiving sheet where the image is formed by a thermal transfer printer, a laser thermal transfer printer and others (any printer that can print on transfer paper such as an ink-jet printer) and the paper for the image to be transferred and passing it between a pair of heat rollers.
In case the printing of multiple copies is performed based upon a color manuscript, a printout is acquired after proof print is performed and finishing is verified. At this time, in a proof print process, a color proof is prepared and is verified. Such a color proof is acquired by transferring an image formed on an image receiving sheet on paper by an image transfer device after the image is formed on the image receiving sheet by a thermal printer and others.
FIG. 6 shows a general image transfer device that can be also used in the invention. As shown in FIG. 6, a reference number 1 denotes an image transfer device, lower and upper heat rollers 41 and 42 are provided opposite in the image transfer device 1, and lower and upper nip rollers 51 and 52 are provided opposite downstream. A heat cover 4 covers the periphery of the heat rollers 41 and 42 to prevent the heat dissipation of the heat rollers 41 and 42 and further, a transfer cover 5 for protection including the nip rollers 51 and 52 covers the outside. An insertion table 2 is provided on the side of an entrance of the image transfer device 1 and in the meantime, an ejection table 3 is provided on the side of the ejection.
Each heat roller 41, 42 is made of aluminum for example, the peripheral surface is coated with a coating layer made of rubber and others and a heater is provided in the center of each heat roller 41, 42. Of the lower and upper heat rollers 41 and 42 provided opposite, one (for example, the lower roller) is for driving and the other roller (the upper roller) is driven. Overlapped paper and image receiving sheet are passed between the lower and upper heat rollers 41 and 42, being heated and pressed, an image on the image receiving sheet is transferred on the paper, afterward, image receiving sheet base material and others are manually peeled from the paper and the image on the paper is acquired.
FIG. 7 is an explanatory drawing for explaining the shape and others of the pair of heat rollers 41 and 42 shown in FIG. 6 in detail. The heat roller 41 is a driving roller of a straight type having the length of 400 [mm]. That is, each diameter xcfx861L and xcfx861R of both ends of the heat roller and the diameter xcfx861C of the central part are all equal, such as a cylindrical type 35.8 [mm] in diameter for example. The heat roller 42 is a driven roller of a crown type having the length of 400 [mm]. That is, the diameter xcfx862C of the central part is slightly longer than each diameter xcfx862L and xcfx862R, 35.8 [mm] for example, of both ends of the heat roller such as a barrel type 36.1 [mm] in diameter for example. Each heat roller 41, 42 is coated with silicone rubber 60 degrees in hardness (JIS hardness A).
Also, the force of 200xc2x140 [N] is respectively applied to both ends of the upper heat roller 42 as pressure P.
Even if the center is slightly bent because each heat roller 41, 42 is supported by only both ends, uniform pressure can be applied to any part of each heat roller 41, 42 because of the combination of the straight type and the crown type.
Heretofore, an image was transferred by using such an image transfer device 1 by the following two methods.
1. In one method, an image receiving sheet R is overlapped on paper P, the overlapped sheet and paper are passed between the pair of heat rollers 41 and 42 as they are and an image of the image receiving sheet R is transferred on the paper P as shown in FIG. 8.
That is, as shown in FIG. 8, when the overlapped paper P and image receiving sheet R on the paper P are passed between the lower and upper heat rollers 41 and 42, they are passed, being heated and pressed, an image of the image receiving sheet R is transferred on the paper P, the paper is carried by the nip rollers 51 and 52 and is ejected onto the ejection table 3.
However, in this case, when the overlapped sheet and paper are passed, they are curved and irregular wrinkles are made. It is conceivable that the wrinkles or windings are made by difference in material between the paper P and the image receiving sheet R in expansion and contraction, in the coefficient of thermal expansion, in the coefficient of moisture absorption between the paper P and the image receiving sheet R.
2. To solve such a problem, this applicant developed a method of using an image transfer device carrier as another method. FIG. 9 shows a transfer method of using this image transfer device carrier.
As shown in FIG. 9, a reference number 9 denotes an image transfer device carrier. The image transfer device carrier includes a carrier board 91 made of aluminum 0.3 [mm] thick, a cover sheet 92 covering only the vicinity of the end in a traveling direction of the carrier board 91 and made of polyimide 0.2 [mm] thick and a heat-resistant tape 93 for fixing the cover sheet 92 to the carrier board 91.
When the image transfer device carrier 9 is used, the cover sheet 92 is first lifted, overlapped paper P and image receiving sheet R are inserted between the cover sheet 92 and the carrier board 91. Next, the cover sheet 92 is returned to the original position and the overlapped image receiving sheet and paper are passed between the pair of heat rollers 41 and 42 with the surface and the back of the overlapped image receiving sheet and paper held between the pair of heat rollers and the side of the heat-resistant tape 93 at the head.
As the paper P and the image receiving sheet R are passed between the heat rollers 41 and 42 with the paper and the image receiving sheet held between the carrier board 91 and the cover sheet 92 and in the image transfer device carrier 9 when the image transfer device carrier is used as described above, the problem of windings is solved.
However, though the problem of windings is solved when the image transfer device carrier 9 is used as described above, the transmission of heat is deteriorated because heat is absorbed in the aluminum board, therefore the velocity of passage is required to be slowed up to approximately {fraction (1/10 )} of conventional passage speed or the temperature of the heat roller is required to be set so that it is higher, compared with the proper temperature, used electric power is increased, the heat insulated structure becomes large-scale and the heat-proof temperature of used members is required to be raised.
Also, as the image transfer device carrier 9 is normally made of aluminum, a carriage path cannot be bent and the miniaturization of the whole device is prevented.
Then, this applicant further invented an image transfer method and an image transfer device thereof in which no winding is made and in addition, the quantity of used electric power is normal at normal passage speed respectively without using the image transfer device carrier formerly and applied as U.S. patent application Ser. No. 09/639,161.
Thereby, in an image transfer device that overlaps an image receiving sheet where an image is formed and paper for the image to be transferred, passes them between a pair of heat rollers from an insertion table and transfers the image formed on the image receiving sheet on the paper, the image receiving sheet is first put on the insertion table, and paper overlapped on the image receiving sheet and the image receiving sheet are inserted between the pair of heat rollers.
Referring to FIG. 2, the image transfer method according to the background art will be briefly described below.
As shown in FIG. 2, a reference number 1 denotes an image transfer device. The image transfer device includes a pair of heat rollers 41 and 42, a heat cover 4 for covering the heat rollers 41 and 42, a pair of nip rollers 51 and 52, a protective cover 5 that covers the heat cover 4 and the pair of nip rollers 51 and 52, an insertion table 2 and an ejection table 3. Also, another pair of nip rollers may be provided outside the heat cover 4 on the upstream side of the pair of heat rollers 41 and 42 and hereby, the overlapped image receiving sheet and paper can be securely nipped. Also, the pair of nip rollers 51 and 52 can be also omitted.
R on the insertion table 2 of the image transfer device 1 denotes an image receiving sheet where an image is formed and P overlapped on the image receiving sheet R denotes paper for the image to be transferred. That is, according to the image transfer method according to the background art, as shown in FIG. 5, relationship between the paper and the image receiving sheet is reverse to the conventional relationship. In the conventional image transfer method shown in FIG. 8, the image receiving sheet R where an image is formed is overlapped on paper P for the image to be transferred, however, to the contrary, in the background art, that paper P is overlapped on the image receiving sheet R. As described above, as paper often including humidity is put on the upper side when the image receiving sheet R is first put on the insertion table 2 and is inserted into the image transfer device with the paper P overlapped on the image receiving sheet R, moisture included in the paper becomes water vapor and gets away upward even if the paper is heated by the heat rollers 41 and 42 and no wrinkle or windings is made.
In this case, as to positional relationship between the image receiving sheet R and the paper P, it is desirable that the paper P is inserted by L1 (L1=21 [mm]) or more before the image receiving sheet R as shown in FIG. 2. Hereby, only the paper P is passed previously, next a part of the paper overlapped with the image receiving sheet R is passed and failure of paper feed (normally called a jam) is reduced.
As described above, according to the background art, as moisture included in the paper gets away upward by putting the paper on the upper side, wrinkles or windings are hardly caused.
However, particularly in case environmental humidity is 60[%] or more and high, wrinkles or windings may be caused on thin paper the basis weight of which is 90 [g/m2] or less.
In view of the foregoing problems, an object of the invention is to provide an image transfer method and a carrier sheet, which is prevented from such wrinkles or windings being made.
To solve the problem, an image transfer method according to a first aspect of the invention is based upon an image transfer method of overlapping an image receiving sheet where an image is formed and paper for the image to be transferred, passing them between a pair of heat rollers and transferring the image formed on the image receiving sheet on the paper and is characterized in that paper overlapped with an image receiving sheet and a hygroscopic or moisture permeable flexible carrier sheet further overlapped on them are inserted between a pair of heat rollers.
Also, an image transfer method according to a second aspect of the invention is characterized in that a flexible carrier sheet the basis weight of which is larger than that of paper is used.
An image transfer method according to a third aspect of the invention is characterized in that fixer which fixes the end of paper is provided to the end of the flexible carrier sheet and for the fixer, concretely, according to a fourth aspect of the invention, a repealable and rebondable adhesive is applied to at least the end of the flexible carrier sheet, according to a fifth aspect of the invention, a holder for holding the end of paper is fixed to the end of the flexible carrier sheet, according to a sixth aspect of the invention, for a concrete example of the holder, an adhesive tape is used and according to a seventh aspect of the invention, the end of the flexible carrier sheet is bent.